Process for producing polymers having oxetanyl group on side chain

ABSTRACT

Polymers having an oxetanyl group on the side chain and being represented by the following formula (2) are provided. They are usable for reactions such as ring-opening reaction and addition reaction. The process comprises subjecting to anionic ring-opening polymerization a 3-[(oxiranylmethoxy)methyl]oxetane monomer represented by the following formula (1) alone or together with other monomer containing an epoxy group:  
                 
 
     wherein A represents a hydrogen atom or an alkyl group of 1-6 carbon atoms,  
                 
 
     wherein A is the same as above, and R represents a hydrogen atom, a chloromethyl group, straight chain alkyl group or branched chain alkylene group of 1-12 carbon atoms, phenyl group, straight or branched chain alkyloxymethyl group of 1-12 carbon atoms or phenoxymethyl group, and n and m each represent a molar fraction, n being 100-1 mol %, m being 0-99 mol % with n+m=100.

BACKGROUND OF THE INVENTION

[0001] The present invention relates to a process for producing polymerscontaining an oxetanyl group on the side chain which are utilizable forvarious reactions such as ring-opening polymerization and additionreaction. Furthermore, the polymers obtained by the process of thepresent invention can be used, for example, as a main component ofultraviolet-curing compositions which cure upon irradiation withultraviolet rays.

[0002] The ultraviolet-curing techniques are very important in theindustries such as coating for wood, coating for metals and printingtaking advantage of high curing rate, good operability with requiringusually no solvents and very small energy quantity needed. Especially,it is known that ultraviolet-curing resins having an oxetane ring whichis a 4-membered cyclic ether are much higher than epoxy resins in curingrate when irradiated with ultraviolet rays. Furthermore, it is expectedthat, when polymers represented by the formula (2) mentioned hereinafterwhich have an oxetanyl group on the side chain, said group having largering-opening polymerizability, are used for ultraviolet-curing resins,the resulting resins are excellent in surface hardness and heatresistance.

[0003] The above polymers having an oxetanyl group on the side chain areproduced by ring-opening polymerizing 3-[(oxiranylmethoxy)methyl]oxetanemonomers represented by the formula (1) referred to hereinafter whichcontain an oxetane ring and an oxirane ring in the molecule. However,hitherto only cationic polymerization was employed and, therefore, boththe oxirane ring and the oxetane ring simultaneously undergoring-opening. As the result, the desired polymers having an oxetanylgroup on the side chain are obtained in only very small yields.

SUMMARY OF THE INVENTION

[0004] An object of the present invention is to provide a process forproducing, in high yields, polymers having an oxetanyl group on the sidechain which can perform various reactions such as ring-openingpolymerization and addition reaction.

[0005] The inventors have found that polymers having an oxetanyl groupon the side chain and represented by the formula (2) can be produced bysubjecting to anionic ring-opening polymerization a3-[(oxiranylmethoxy)methyl]oxetane monomer represented by the formula(1) alone or together with other monomers having an epoxy group.

[0006] wherein A represents a hydrogen atom or an alkyl group of 1-6carbon atoms.

[0007] wherein A is as defined above, and R represents a hydrogen atom,a chloromethyl group, straight chain alkyl group or branched chainalkylene group of 1-12 carbon atoms, phenyl group, straight or branchedchain alkyloxymethyl group of 1-12 carbon atoms or phenoxymethyl group,and n and m each represent a molar fraction, n being 100-1 mol %, mbeing 0-99 mol % with n+m=100.

BRIEF DESCRIPTION OF THE DRAWINGS

[0008]FIG. 1 shows a proton nuclear magnetic resonance spectrum of3-ethyl-3-[(oxiranylmethoxy)methyl]oxetane.

[0009]FIG. 2 shows a proton nuclear magnetic resonance spectrum of thepolymer obtained in Example 1.

[0010]FIG. 3 shows conversion vs. irradiation time curves forpolymerization in Reference Example 1.

[0011]FIG. 4 shows conversion vs. irradiation time curves forpolymerization in Reference Example 2.

DETAILED DESCRIPTION OF THE INVENTION

[0012] The present invention is based on the discovery that when3-[(oxiranylmethoxy)methyl]oxetane monomers represented by the formula(1) which are compounds having an oxetane ring and an oxirane ring inthe molecule (hereinafter referred to as “oxetanyl group-containingmonomers”) are ring-opening polymerized by anionic polymerization, theoxatene ring remains as it is and only the oxirane ring is ring-openingpolymerized.

[0013] The oxetanyl group-containing monomers used in the presentinvention are prepared by a reaction of 3-hydroxymethyloxetanerepresented by the formula (3) with epichlorohydrin represented by theformula (4) in high yields.

[0014] wherein A represents a hydrogen atom or an alkyl group of 1-6carbon atoms.

[0015] If necessary, the oxetanyl group-containing monomer used in thepresent invention may be copolymerized with monomers containing an epoxygroup (hereinafter referred to as “epoxy monomer”). As the epoxymonomers, there may be used various ones which have anionicpolymerizability, such as ethylene oxide, epichlorohydrin, straightchain or branched chain alkylene oxides of 1-12 carbon atoms, styreneoxide, straight chain alkylglycidyl ethers or branched chainalkyleneglycidyl ethers of 1-12 carbon atoms and phenylglycidyl ether.

[0016] A process for producing polymers having an oxetanyl group on theside chain in the present invention comprises subjecting the oxetanylgroup-containing monomer or a mixture of the oxetanyl group-containingmonomer and the above-mentioned epoxy monomers at an optional ratio toanionic ring-opening polymerization in order to selectively ring-openingpolymerize only the oxirane ring in the oxetanyl group-containingmonomers and epoxy monomers.

[0017] The conditions of the anionic ring-opening polymerization are notcritical. Any conditions generally employed may be applied. For example,as polymerization initiators, there may be used alkali metal hydroxidessuch as sodium hydroxide or potassium hydroxide, or alkali metalalcoholates such as sodium methylate or t-butoxypotassium. They aregenerally used for ring-opening polymerization of oxirane ring.Preference is t-butoxypotassium, because polymerization rate is large.An amount of the polymerization initiators is suitably 0.01-100 mmolsfor 1 mol of the monomer.

[0018] The anionic ring-opening polymerization can be carried out in thepresence or absence of solvents. Preferably, the polymerization iscarried out in the absence of solvents in view of the largepolymerization rate.

[0019] Polymerization temperature for the anionic ring-openingpolymerization is preferably −78° C.-150° C., more preferably 0° C.-80°C., depending on reactivity of the monomers used.

[0020] A period of time for polymerization varies depending onreactivity of monomers used and polymerization temperature, preferably10 minutes to 20 hours.

[0021] The resulting polymers are purified by the generally employedwashing, re-precipitation and the like.

[0022] The present invention will be explained specifically by thefollowing examples.

EXAMPLE 1

[0023] Reagent used: 3-Ethyl-3-[(oxiranylmethoxy)methyl]oxetane(hereinafter referred to as “GlOx”) subjected to distillation in thepresence of CaH₂

[0024] Catalyst: Commercially available t-butoxypotassium (hereinafterreferred to as “t-BUOK”) subjected to sublimation

[0025] Solvent: THF subjected to distillation in the presence ofsodium-benzoquinone

[0026] Polymerization method:

[0027] t-BUOK (23 mg, 0.205 mmol) was charged in one tube of an H-shapedtube made of glass and GlOx (1.14 g, 4.19 mmols) was charged in anothertube in the presence of dry nitrogen. THF (2.1 ml) was added to thecatalyst, and, then, the polymerization tube was sealed and kept at 60°C. Polymerization was started by mixing both the solutions. (Thepolymerization system showed light yellow color immediately after thepolymerization, but did not gel.) After lapse of 48 hours, the reactionproduct was poured into a large amount of methanol in order to terminatethe polymerization. Methanol was distilled off, followed by carrying outre-precipitation twice with a mixture of chloroform and n-hexane.Thereafter, the undissolved portion was dissolved in chloroform,followed by washing with water. Chloroform was distilled off, followedby carrying out azeotropy twice with benzene to obtain a polymer (0.73g, 64.1%).

[0028] The resulting polymer was a viscous substance (light yellow)soluble in methanol, THF, chloroform or toluene, and insoluble inn-hexane.

EXAMPLE 2

[0029] Example 1 was repeated, except that toluene subjected todistillation in the presence of sodium-benzoquinone was used as thesolvent.

EXAMPLE 3

[0030] Example 1 was repeated, except that the polymerization wascarried out in the absence of the solvent.

EXAMPLES 4 AND 5

[0031] Example 1 was repeated, except that the polymerization wascarried out in the absence of the solvent, but phenylglycidyl ether(hereinafter referred to as “PGE”) subjected to distillation in thepresence of CaH₂ was used as a comonomer.

[0032] The results are shown in Table 1. TABLE 1 Number- G1Ox PEGSolvent Initiator Yield average Example (g) (g) (ml) (mg) (%) weightMw/Ma 1 1.14 0 THF (2.1) t-BuOK (23) 64.1 5,420 1.62 2 1.14 0 Toluene(2.1) t-BuOK (23) 72.2 5,150 1.42 3 1.14 0 None t-BuOK (23) 94.2 9,4001.20 4 1.72 13.52 None t-BuOK (56) 87.3 12,800 1.66 5 5.17 10.51 Nonet-BuOK (56) 93.5 12,760 1.83

[0033]FIG. 1 and FIG. 2 show proton nuclear magnetic resonance spectrumof GlOx used as the monomer and that of the polymer obtained inExample 1. The peaks of the hydrogen atoms on the oxetane ring which arepresent at 4.3-4.4 ppm in FIG. 1 appear also in FIG. 2, while the peaksof the hydrogen atoms on the epoxy ring which are present at 2.5-3.5 ppmin FIG. 1 completely disappears in FIG. 2. From this fact, it is clearthat in the Example, only the epoxy group was selectively polymerized togive a polymer containing an oxetanyl group on the side chain.

REFERENCE EXAMPLE 1 Photocationic Polymerization of a Polymer Having anOxcetanyl Group in a Side Chain

[0034] A mixture of the polymer having an oxcetanyl group in a sidechain and being obtained in Example 1 and diphenyl-4-thiophenoxyphenylsulfonium hexafluoroantimonate, a photopolymerization initiator (0.5 mol%), was coated (10 μm thick) on an aluminium plate. Ultra-violet rayirradiation were effected under intensities of 21.2 and 123 mW/cm²,respectively, in order to proceed with polymerization. Decrease in anoxetane ring was measured by infrared radiation (995 cm⁻¹) in order toobserve polymerization degree.

[0035] The results are shown in FIG. 3 wherein ο and Δ relate to UVintensities of 21.2 mW/cm² and 123 mW/cm², respectively. In FIG. 3,decrease in an oxetane ring reaches 40-50% and polymerization of thepolymer having an oxcetanyl group in a side chain is seen.

REFERENCE EXAMPLE 2 Photocationic Polymerization between a PolymerHaving an Oxcetanyl Group in a Side Chain and a Compound Having an EpoxyGroup

[0036] Reference Example 1 was repeated except that phenyl glycidylether (10 mol %) was added to the mixture, and ultra-violet rayirradiation was effected under intensity of 21.2 mW/cm² only.

[0037] The results are shown in FIG. 4 wherein ο and  relate to thepolymer obtained in Example 1 and the polymer between the polymerobtained in Example 1 (90) and phenyl glycidyl ether (10). FIG. 4 showsthat decrease in an oxetane ring is larger and polymerization occursmore violently, due to co-presence of a compound having an epoxy group.

[0038] According to the process of the present invention, polymershaving an oxetanyl group on the side chain which can perform variousreactions such as ring-opening polymerization and addition reaction canbe produced economically and advantageously. For example, when thepolymers are used in ultraviolet-curing compositions which cure uponirradiation with ultraviolet rays, the compositions can be rapidly curedby irradiation with light in a short period of time, and the curedproducts are excellent in adhesion, heat resistance and chemicalresistance. The polymers are useful for such coating or printingmaterials as ink or paint.

1. A process for producing a polymer having an oxetanyl group on theside chain and represented by the following formula (2) which comprisessubjecting to anionic ring-opening polymerization a3-[(oxiranylmethoxy)methyl]oxetane monomer represented by the followingformula (1) alone or together with other monomer containing an epoxygroup:

wherein A represents a hydrogen atom or an alkyl group of 1-6 carbonatoms,

wherein A is the same as above and R represents a hydrogen atom, achloromethyl group, straight chain alkyl group or branched chainalkylene group of 1-12 carbon atoms, phenyl group, straight or branchedchain alkyloxymethyl group of 1-12 carbon atoms or phenoxymethyl group,and n and m each represent a molar fraction, n being 100-1 mol %, mbeing 0-99 mol % with n+m=100.
 2. A process according to claim 1,wherein the other monomer containing an epoxy group is ethylene oxide,epichlorohydrin, a straight chain or branched chain alkylene oxide of1-12 carbon atoms, styrene oxide, straight chain alkylglycidyl ether orbranched chain alkyleneglycidyl ether of 1-12 carbon atoms orphenylglycidyl ether.
 3. A process according to claim 1, wherein analkali metal hydroxide or alkali metal alcoholate is used as apolymerization initiator.
 4. A process according to claim 3, wherein thepolymerization initiator is t-butoxypotassium.
 5. A process according toclaim 1, wherein the anionic ring-opening polymerization is carried outin the absence of a solvent.
 6. A process according to claim 1, whereinthe anionic ring-opening polymerization is carried out at a temperatureof −78° C. to 150° C.
 7. A process according to claim 1, wherein theanionic ring-opening polymerization is carried out for 10 minutes to 20hours.